I don't have any experience with the integrations you mentioned but I have used Bill.com for A/P for a couple of years and am very happy with it. If your goal is inputting, approving, and tracking invoices, it works wonderfully for that purpose. It fully integrates with QB Desktop via a sync tool. We have several users set up in Bill.com and our workflow is this: User1 reconciles the bill, User2 enters the bill and User3 approves and pays the bill. There is no limit on storage space in terms of bills, documents, etc. so we use it for all sorts of electronic storage as it applies to our vendors. Their customer support is exclusively online chat and I've found it to be quite good.
We pay exclusively through Bill.com except for our Canadian vendors. Bill.com prints and mails the checks and handles the electronic payments based on our preferences. The cost is approximately $250/month, but I rarely ever print, sign and mail payments anymore. Checks sent to vendors via mail come from Bill.com's bank account so there's some security knowing your routing and bank account numbers aren't exposed to your vendor's A/R department. If I had to estimate, I'd say our A/P processing time has dropped about 40%.